textproduct: Albany

WHAT HAS CHANGED

Shower and thunderstorm coverage this morning into early this afternoon has been greater than previously expected. As a result, we have not yet begun to destabilize. Therefore, the window hosting the greatest probability for severe thunderstorms has shifted to about 4 PM to 11 PM in alignment with the best forcing. This will significantly limit the time available for destabilization to occur even if we get the breaks of sun necessary to achieve it. An additional limiting factor to that will be smoke coverage from the Canadian wildfires, which is already inhibiting heating upstream. Bottom line, confidence in the severe weather threat and coverage of potential severe thunderstorms has significantly decreased for today.

KEY MESSAGES

1) An Enhanced (Level 3 of 5) to Slight Risk (Level 2 of 5) for severe weather remains for this afternoon through this evening across eastern New York and western New England, though confidence in the severe weather potential and coverage has significantly decreased.

2) A Moderate (Level 1 of 4) to Slight Risk (Level 1 of 4) for flash flooding remains in effect this afternoon through this evening. While isolated flash flooding is possible, urbanized ponding and nuisance flooding will be more likely.

3) Dry conditions return for the end of the weekend into the beginning of next week before additional chances for showers and thunderstorms swiftly return beginning Tuesday.

DISCUSSION

KEY MESSAGE 1...

Widespread showers and non-severe thunderstorms have been ongoing across the region over the last several hours along and ahead of a warm frontal boundary associated with a deepening surface cyclone that is currently straddling the border of southeast Ontario and southwest Quebec. Aloft, a potent, mid-level shortwave is digging through the eastern Great Lakes/Ohio River valley with a southwest moisture plume at its leading edge helping to drive precipitation amounts of 0.1" to nearly 1" thus far. Based on latest radar/satellite trends, a small dry slot is swiftly approaching directly in the wake of the warm front, which is making its eastwardly track through our region now. Within this dry slot lies our best shot at destabilization.

Visible satellite shows modest clearing across portions of western New York where the warm sector of the aforementioned frontal system is beginning to advect into. Latest SPC Hourly Mesoscale Analysis shows that SBCAPE has quickly surged to 2000-3500 J/kg in these areas courtesy of strong warm air and moisture advection driving temperatures into the upper 70s to mid 80s and dewpoints into the low to mid 70s. Throughout the Ohio River Valley and into the western Mid-Atlantic, where little to no precipitation has occurred thus far today and where the heart of the warm sector sits, convection is firing off on all cylinders with highly unstable conditions and strong shear. These obs are potentially indicative of a couple things. First, destabilization is happening very quickly with breaks in cloud coverage. One of the potential limiting factors of convection heading into today was going to be the presence of wildfire smoke, as it was thought that it could limit daytime heating. That said, latest GeoColor imagery shows very little smoke across most of the Northeast. So, if we do get some breaks of cloud cover within the dry slot, we could see an increase in instability fairly quickly. That could increase the potential for severe weather this afternoon. However, based on the fairly extensive cloud cover that we still have across the area, we will likely have a very limited window of time to destabilize sufficiently before the next round of convection comes in. The second is that not only could our potential for destabilization be limited by our own early convection and current appreciable cloud cover, but by the convection happening all around us. Heavy rain with some fairly long-lived, non-severe thunderstorms to our west, south, and southwest this morning into early this afternoon has more than likely robbed us of some of the energy and moisture that would have otherwise been available. Therefore, this could not only pose an inhibition of severe convection this afternoon/evening, but limit the magnitude of severity should we get any severe storms.

Confidence is therefore low in the overall threat for severe thunderstorms this afternoon and evening despite the Enhanced (level 3 of 5) to Slight (level 2 of 5) Risks for severe weather that remain in place. What we have high confidence in, is another round of showers and thunderstorms driven by increased forcing this afternoon into this evening. Latest guidance indicates a pre-frontal trough beginning its track through the region between about 4-6 PM. As this feature progresses, the parent low will continue to deepen and track northeastward beneath the still deepening shortwave aloft. Strengthening warm air and moisture advection associated with the 30- 45kt, 850hPa LLJ within the warm sector will ultimately pair with the increased forcing to generate clusters of showers and thunderstorms that should move through the region from northwest to southeast from about 4 PM this afternoon to 2 AM tomorrow morning. With an increasing wind field aloft, the right entrance region of the upper-level jet moving overhead, and 30-50kt of 0-6km shear in place, some level of linear organization is certainly possible. Gusty winds are subsequently likely from any shower or thunderstorm that develops. However, if we don't get the instability needed to drive severe magnitude, damaging wind gusts will not be plausible.

KEY MESSAGE 2...

The latest NYS Mesonet indicates about 0.1" to nearly 1" of rain has fallen across the region thus far today with the greatest amounts observed within portions of the Mohawk Valley, Upper- Hudson Valley, and Mid-Hudson Valley/Taconics. The Weather Prediction Center has maintained the Slight Risk (level 2 of 4) for flash flooding for the Mid-Hudson valley and portions of southwestern New England through tonight with a Marginal Risk (level 1 of 4) elsewhere. While another round of showers and thunderstorms is anticipated this afternoon with embedded moderate to heavy downpours, latest forecast soundings indicate very fast storm motions which should mitigate the threat for flash flooding in most cases. That said, the aforementioned areas that have had the most rain so far today will hold the greatest risk of isolated flash flooding should they get hit again with additional showers and thunderstorms this afternoon and evening. But, with dry antecedent conditions and 1 hr FFG around 2" to nearly 3" per hour, there is a low probability of even isolated flash flooding across the region.

KEY MESSAGE 3... Once the cold front associated with the aforementioned low pressure system moves through the region tonight, dry conditions will regain hold of the region to finish out the weekend and begin the new work week. Temperatures will even be pleasantly just below or near seasonable through this week, so there are no concerns for oppressive heat at this time. That said, additional chances for showers and thunderstorms will come beginning Tuesday as we remain in a broad trough pattern through much of the week. Tuesday into Wednesday look to be the wettest days at this time with the potential for additional severe thunderstorms Tuesday depending on the timing of the next frontal system.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 18z Sunday...Numerous showers and embedded storms have developed across the area, all in associated with a warm front that is lifting through the area. While VSBY restrictions have occurred with this activity, stronger, more concentrated thunderstorm activity is expected later this afternoon ahead of the the main cold front that will move through later tonight. Storms, out ahead of the cold front, should track from NW to SE between 21z to 02z. There remains high enough confidence to mention TEMPOs at all TAF sites for the TSRA, with strong winds and IFR conditions. Conditions will also lower to MVFR/IFR this evening as a cold front moves across the region, then gradually improve towards 12z Sunday. Winds will become southerly and increase to 10-15 kt after the warm front passes, however stronger gusts will likely remain confined to thunderstorm activity.

Outlook...

Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: High Operational Impact. Breezy. Likely SHRA...TSRA. Tuesday Night: High Operational Impact. Definite SHRA...TSRA. Wednesday: High Operational Impact. Definite SHRA...TSRA. Wednesday Night: Low Operational Impact. Slight Chance of SHRA. Thursday: Low Operational Impact. Slight Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Air Quality Alert until midnight EDT tonight for CTZ001-013. NY...Air Quality Alert until midnight EDT tonight for NYZ032-033- 038>043-047>054-058>061-063>066-082>084. MA...Air Quality Alert until midnight EDT tonight for MAZ001-025. VT...Air Quality Alert until 11 PM EDT this evening for VTZ013>015.